Structural effects on third order nonlinear optical properties of PPV derivatives

The third order nonlinear optical properties of a series of poly(p-phenylenevinylene) (PPV) derivatives were measured on thin film by the Third Harmonic Generation technique, in the infrared range between 1.2 mum and 2.1 mum useful for optical telecommunications applications, in order to study the effect of various structural parameters on the third order nonlinear optical coefficient chi((3))

In situ growth in a PMMA film of oriented nanocrystals of the hybrid inorganic-organic acentric material [(E)-N,N-dimethylamino-N '-methylstilbazolium][Cu(5)I(6)]

A poly(methyl methacrylate) (PMMA) composite film containing 4 wt% of the strongly second order NLO active ionic material [(E)-N,N-dimethylamino-N'-methylstilbazonium][Cu(5)I(6)] (1), obtained by spin coating of a CH(3)CN solution on a glass substrate, shows by a two step process (electric poling followed by controlled thermal annealing up to 140 degrees C) in situ growth of nanocrystals, some of which are aligned, with a size of less than 400 nm as supported by TEM and GIXRD evidence. A long lasting second harmonic generation (SHG) is produced which is stable even after exposure to water vapour for one night

Advanced spectroscopies of graphene and 2D materials

A full exploitation of the unique features of graphene and related 2D materials in micro and nano-scaled optoelectronic devices for high-data rate photonic systems calls for a deep understanding of their fundamental structural, electronic, photophysical properties and fast dynamics. We introduce some advanced spectroscopic techniques developed to this aim, while reviewing their specific potentialities and highlighting recent results. To provide absolute local nanoscale thickness metrology of as-grown 2D materials, Scanning Auger Electron Microspectroscopy has been calibrated. Results obtained for graphene and graphene oxide (GO) are reported, showing sub-monolayer resolution. Ultrafast optical transient absorption spectroscopy, with temporal resolution down to 10fs, unveils the relaxation dynamics of hot electrons in single layer graphene and the formation and radiative recombination via stimulated emission of biexcitons in ultra-narrow, structurally well-defined nanoribbons (GNRs). By recently developed ultrafast Time- and Angle-resolved Photo-Electron Spectroscopy (TR-ARPES) we investigate electronic states and spin dynamics close to the Dirac cone, in graphene and metal chalcogenide topological insulators (TI) under fs strong laser excitation, in view of spintronic applications